Continuous Antegrade Blood Cardioplegia:
Cold vs. Tepid

Abstract

Background: Continuous antegrade blood cardioplegia (CABCP) is used at different temperatures. We investigated the consequences of CABCP at 6 °C (COLD) vs. 28 °C (TEPID). Methods: Anesthetized open-chest pigs (25 ± 2 kg) were placed on cardiopulmonary bypass (CPB). The hearts were arrested for 30 min by 6 °C cold or 28 °C tepid CABCP (n = 8 each). After an initial 3 min antegrade application of high potassium (20 mEq) cold (6 °C) blood cardioplegia, the hearts were arrested for a subsequent 27 min by normokalemic blood delivered antegrade at either 6 °C or 28 °C. After this, the hearts underwent perfusion with warm systemic blood for an additional 30 min on CPB. Biochemical cardiac data (MVO₂ [ml/min/100 g], release of creatine kinase [CK U/min/100 g] and lactate [mg/min/100 g]) were measured during CPB. Total tissue water content (%) and left ventricular stroke work index (SWI g × m/kg) were determined 30 min after discontinuation of CPB and compared to pre-CPB controls. Results: Cold CABCP kept all hearts continuously arrested. The COLD hearts showed no biochemical or functional disturbance. The TEPID hearts intermittently fibrillated and required additional high potassium BCP shots. The TEPID hearts showed a marked CK leakage (2.6 ± 0.4* vs. 0.7 ± 0.4), lactate production (4.0 ± 1.6* vs. extraction from the COLD group) despite the non-ischemic protocol, an impaired initial oxygen consumption (4.2 ± 1.3 vs. 7.1 ± 1.6) at the end of cardiac arrest, the formation of myocardial edema (79.5 ± 1.0* vs. 77.0 ± 0.8), and a depressed recovery of SWI (0.69 ± 0.15° vs. 1.41 ± 0.13). *p < 0.05 for comparison of TEPID vs. COLD hearts using Student's t-test for unpaired data; °p < 0.05 for intergroup-comparison of TEPID vs. COLD vs. controls using ANOVA adjusted for repeated measures. Conclusions: Uninterrupted cardioplegia can be safely performed with cold normokalemic CABCP. In contrast, tepid normokalemic CABCP leads to fibrillation, jeopardizes the heart, and should be avoided.

Temperature - Cardioplegia - Myocardial protection - Cardiopulmonary bypass - Heart surgery

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